The invention relates to a method for monitoring a communications link, in particular a telephone call, between two communications subscribers. At least one of the subscribers is a subscriber which is to be monitored, the identifier (for example the IN call number or xe2x80x9cPersonal User Identityxe2x80x9d) of the subscriber or subscribers which is/are to be monitored, or of a subscriber which is to be monitored, being flagged. The flagging containing an indication of which third communications subscriber or subscribers is/are to be authorized to monitor a communications link to the subscriber which is to be monitored. If a subscriber which is to be monitored is called or calls a second communications subscriber, a conference circuit between the subscriber which is to be monitored, the calling or called second communications subscriber and a third communications subscriber which is authorized to monitor is set up.
National and international laws require that operators of a public, and in the future probably also of a private, network should permit so-called authorized agencies (criminal police, secret service etc.) to monitor the communications traffic of persons under suspicion, in compliance with certain legal regulations for the protection of communications subscribers (for example court orders). While this is relatively easy to do in the local exchange of the subscriber which is to be monitored in the case of conventional fixed-line telephone networks by flagging the corresponding subscriber data record and setting up a type of conference circuit to the authorized agency, in intelligent networks (IN) there is a basic problem. This results from the division of functions of signaling and of voice traffic between different network components. In the case of IN calls, it is generally not defined in advance which exchanges (VSt) calls of a subscriber which is to be monitored will pass through. In addition, all the data which are required for the monitoring operation (including IN numbers and fixed-network call numbers of the communications parties) are not available at the same location.
International Patent Disclosure WO 97/41678 has already specified a method for monitoring a communications link which is suitable for communications services with IN services.
It is accordingly an object of the invention to provide a method for monitoring a subscriber of an intelligent network which overcomes the above-mentioned disadvantages of the prior art methods of this general type, in which an improved method for monitoring a communications link is specified.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method for monitoring subscribers of an intelligent network, which includes:
flagging an identifier of a subscriber to be monitored in a central database, the flagging containing an indication of which third communications subscribers is authorized to monitor a communications link of the subscriber to be monitored;
setting up, via an exchange having initiated a link to the central database, a conference circuit between the subscriber which is to be monitored, a calling or called second communications subscriber and at least one of the third communications subscribers which is authorized to monitor if the subscriber to be monitored is calling or is called by the second communications subscriber, and a decision as to whether monitoring of the subscriber to be monitored is initiated by the exchange being taken from the central database or a controller of the intelligent network as a function of a type of access to the controller; and
transferring subscriber data which are characteristic of the subscribers of the intelligent network to the at least one third communications subscribers.
Because the authorized agency is interested in monitoring a communications link only if communication is actually taking place on the link, the invention distinguishes, in a demand-controlled fashion, between two (or even more) different monitoring methods. The significant advantage in comparison with the method that has already been described is the reduction of the loading on the communications network (SS7/INAP interface and exchange).
The method which is known from International Patent Disclosure WO 97/41678 is used according to the invention only if communication actually takes place via the communications link, so-called xe2x80x9ccall related activityxe2x80x9d. This can be determined by the type of access that is made to the service control point (SCP). Here, it is irrelevant whether the communications party is another person or a technical device such as a mailbox. In this case, the following procedure is adopted:
I. The subscriber that is to be monitored is an IN subscriber.
a) The IN number of the subscriber that is to be monitored is flagged in the service control point (SCP). The flagging contains an indication of which authorized agencies are provided with a monitoring facility.
b) In an extension of the IN-specific protocol between the SCP and the service switching point (SSP) (usually in the transit exchange (TE) of the calling subscriber), the SSP is informed that the respective telephone call is to be monitored, and by whom it is to be monitored.
c) A conference circuit to the authorized agency is set up by the exchange in which the SSP is located. The link data (fixed-network call numbers, IN numbers, time, duration of the call) and the content of the call or of the data link are transmitted online to the authorized agency.
II. The communications party of the subscriber that is to be monitored is an IN subscriber.
a) The call number of the subscriber that is to be monitored is flagged in the exchange of the subscriber. The flagging contains an indication of which authorized agencies are provided with a monitoring facility. If the subscriber that is to be monitored is a subscriber in the classic sense, i.e. is not an IN subscriber, the flagging occurs once in the local exchange of this subscriber. If the subscriber that is to be monitored is an IN subscriber, the flagging takes place in accordance with I noted above.
b) The exchange that is mentioned in a) requests from the SSP of the communications party the data that are not present in the exchange (for example the IN number or the fixed-network call number of the communications party).
c) The exchange sets up a conference circuit to the authorized agency. The link data (fixed-network call numbers, IN numbers, time, duration of the call) and the content of the call or of the data link are transmitted online to said authorized agency.
In the other case, if there is no communication, the procedure described above generates a higher degree of loading of the communications network. This is the case, for example, if an IN service is administered by the subscriber which is to be monitored, for example the setting up or changing of a call divert facility (call unrelated activity). It is completely sufficient here if only the event data are transferred from the SCP to the authorized agency without the associated exchange being involved.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a method for monitoring a subscriber of an intelligent network, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.